Embodiments of the present invention relate to a polyamide water-treatment separation membrane and a manufacturing method thereof, and more particularly, to a polyamide water-treatment separation membrane having improved antifouling properties with a coating layer including a specific compound formed on a polyamide membrane, and a manufacturing method thereof.
Osmosis occurs when two solutions of different concentration are isolated by a semi-permeable membrane and solvent flows from a solution having a lower concentration of solute to another solution having a higher concentration of solute. The pressure applied to the solution having the higher concentration of the solute by the movement of the solution is known as osmotic pressure. When a external pressure higher than the osmotic pressure is applied to the higher concentration side, the solvent may move from the solution having the higher concentration of the solute to the solution having the lower concentration of the solute. This phenomenon is known as reverse osmosis. By using the principle of reverse osmosis, various salts and organic materials may be separated by the semi-permeable membrane by using a pressure gradient as a driving force. A water-treatment membrane may be used for separating materials on the molecular level, removing salts from saline water and seawater, and providing water for domestic, commercial and industrial use by using the reverse osmosis phenomenon.
A polyamide membrane is an example of such a water treatment separation membrane. The polyamide water-treatment membrane is manufactured by forming an active polyamide layer on a support having pores with a small pore size. The minute and support having pores may be formed by forming a polysulfone layer on a non-woven fabric, impregnating the minute and support having pores with an aqueous m-phenylenediamine (mPD) solution to form an mPD layer, and impregnating the mPD layer with a trimesoyl chloride (TMC) organic solution so that the mPD layer contacts the TMC to allow for interfacial polymerization and to form a polyamide layer.
Some commercial applications may require certain conditions to be met by a separation membrane. One of the conditions is a high salt rejection rate. A commercially required salt rejection rate for the water-treatment membrane may be 97% or above with respect to brackish water. Other desirable characteristics include high flux by which a relatively large amount of water may be transmitted under a relatively low pressure. In general, the preferred permeation flux of a membrane is about 10 gallons/ft2-day (gfd) under a pressure of 800 psi for sea water, and 15 gfd or above under a pressure of 220 psi for saline water.
Recently, prevention of fouling of a membrane has been recognized as a potential area for improvement along with other characteristics, such as the salt rejection rate and the permeation flux. When a membrane is fouled, floating materials or dissolved materials may be attached to the surface of the membrane. When the fouling occurs, permeation flux may be decreased due to adsorption and growth of microorganisms on the surface of the separation membrane. This may cause secondary pollution such as forming a bio-film on the surface of the separation membrane. Since a polluted separation membrane has decreased permeation properties, frequent corrections of the pressure may be necessary to maintain a constant permeation flux. When the fouling of the membrane is severe, a cleaning process may be required.